21256227521 has 4 divisors (see below), whose sum is σ = 21259710852. Its totient is φ = 21252744192.

The previous prime is 21256227451. The next prime is 21256227557. The reversal of 21256227521 is 12572265212.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 8183735296 + 13072492225 = 90464^2 + 114335^2 .

It is a cyclic number.

It is not a de Polignac number, because 21256227521 - 2³⁴ = 4076358337 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (21256227571) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1732496 + ... + 1744721.

It is an arithmetic number, because the mean of its divisors is an integer number (5314927713).

Almost surely, 2^21256227521 is an apocalyptic number.

It is an amenable number.

21256227521 is a deficient number, since it is larger than the sum of its proper divisors (3483331).

21256227521 is an equidigital number, since it uses as much as digits as its factorization.

21256227521 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3483330.

The product of its digits is 33600, while the sum is 35.

The spelling of 21256227521 in words is "twenty-one billion, two hundred fifty-six million, two hundred twenty-seven thousand, five hundred twenty-one".